I could write a voluminous tractate about this question, but I only want to make some brief inspiring suggestions:
(1) Of course there is the influential role of „social media“ in the early internet age with their non-redactional news channels, often enough untouched by any concern about ethics of journalism, and with their filter-bubbles which via mere quantitative affirmation make it appear like „THE TRUTH“ if you cheaply find what you seek. Important as this connection is, I’d like to direct your attention towards some less talked-about, but equally worth-pondering-about possibilities for explaining the current pandemic of conspiracy ideologies:
(2) People want to be part of a group. In order to contribute to the identity of the person as a member of the group, the identity of the group must be defined by a clear inside and a clear outside. This has become a major problem in the age of diversity. Today, everyone feels almost like „a super-small fringe group of his own“. As objectively validable reality today doesn’t show mercy with persons in need of large clear homogenous group identities concerning any reliable grand ideas anymore, such ideas in the 21st century can only be found off-road the paths of rational and empirical evidence. The 50 years between 1918 and 1968 were the „great“ epoch of ideologies that claimed to be rationally comprehensible; since the breakdown of Soviet Communism in the late 1980s, soon followed by equal disillusion about unbridled capitalism, the whole principle of „strictly reasonable“ (which means hypothetically falsifiable, „non-post-factual“) ideologies has come to an end, leaving behind a painful mental vacuum.
(3) There are a number of „western“ post-modern cultural features, among them certain trends of pedagogy predominant since about 1970, which undoubtedly have contributed to a significant increase of narcissism in western societies. Among the core roots of feelings of narcissistic abasement are uncertain social identity, low-profile (or low-quality) enemy images and not-superior own knowledge. Conspiracy ideologies perfectly serve against all three issues.
(4) An important part of the cultural change since about 1970 is particularly the subsiding of the traditional reverence towards elder people. It is no longer generally accepted that older people are wiser than younger people. However, for psychologists it’s an empirical fact that older people are less inclined to believe conspiracy ideologies than are younger persons. So the societal effect of older people’s influence retaining younger people from believing in conspiracy ideologies has significantly lessened.
(5) In the traditional-religious age, propensity towards conspiracy ideologies has normally been canalized into apocalypticism. Our age is actually still religious, but certainly no longer traditionally religious, compared to all pre-20th-century history. Today, apocalypticism is clearly no major societal option anymore. Conspiracy ideology seems to have superseded apocalypticism especially as a strategy for coping with social trauma: As the fellow human being who is unsettlingly experienced as a personally offensive evildoer can no longer convincingly be interpreted as the devil or as a demon, his conspiracy-ideological interpretation as „an agent of THEM“ becomes the replacement „psycho-valve“ instead.
(6) Inherent to conspiracy ideologies is a certain self-enhancing dynamic; because for many people, the first thing they expect to really be there is not conspiracies, but conspiracy ideologies; in other words, especially in times of crisis, they expect conspiracy lies to be distributed. Ironically or tragically, that expectation contributes to shaking ALL truths, regardless of their quality; because human reason is initially confident that it will be able to check strange assertions out, but by way of experience, especially in chaotic times of crisis, makes the disconcerting discovery that this is by no means often enough satisfyingly possible. So, precisely the initial critical expectation of something untrue can have the paradoxical effect of driving the person into profound confusion about truth.
(7) The core code of all conspiracy ideologies is: „Something just isn’t right.“ empirical psychologists have shown this by demonstrating that persons with a tendency to believe in conspiracy ideologies typically are inclined to equally believe contradicting assumptions, for example, that a famous person has been murdered, or that the same person has faked his or her death. This can only mean that the „feeling“ of „some“ conspiracy is usually more important than the actual exact content of this or that conspiracy ideology. However, times of major crisis always naturally are times in which „something just isn’t right“. Conspiracy believers make the main mistake to easily believe in everything their mind tells them about the allegedly distinctive objective causes of their vague gloomy feelings. You don’t need to be stupid in order to make that mistake; on the contrary, this mistake is particularly likely in persons with a high „technical“ (but merely „technical“) intelligence of the mind, as empirical psychological studies have shown.
But this feeling that „something just isn’t right“ has precisely one particularly prominent average reason: loneliness. The correlation between social isolation and propensity towards conspiracy ideologies is a solid result of latest psychological and sociological empirical research. Out of the diffuse but burdensome feeling that „something just isn’t right“, the answer to the question „What’s wrong?“ is looked for in thought products, while it actually lies in the „simple“ unease of loneliness: As loneliness generally triggers brooding thinking, the loners frequently miss to put their question into its actually „right“ form: „What’s wrong WITH ME?“, and instead, falling victims to their blind spot, begin to obsessively inquire about what’s wrong with the world around them.